1. Field of the Invention
This invention relates to processes for the production of tocotrienol compounds from biological sources such as palm oil, cereals, grains, and grain oils. The tocotrienol products are recovered in high yields. Tocotrienols are useful as pharmaceuticals, in foodstuffs and as dietary supplements. These compositions are hypocholesterolemic, antioxidizing, antithrombotic, antiatherogenic, anti-inflammatory and immunoregulatory in nature. Tocotrienols are known to lower the levels of low density lipoproteins in the bloodstream.
2. Background Art
Tocopherols and tocotrienols (hereinafter “tocols”) are organic compounds that are found in plant material. These compounds are important because they retard the oxidation and spoilage of plant matter. Tocols are also components of vitamin E and possess similar general structural features. Tocols generally have an aromatic chromanol head and a 16-carbon hydrocarbon tail. The number and position of methyl substituents in the chromanol nucleus gives rise to the α-, β-, γ- and δ- homologues. The saturation of the hydrocarbon chain differentiates tocopherols with a saturated chain from tocotrienols with an unsaturated chain as forms of vitamin E. It has also become known that tocols have hypocholesterolemic effects, an important health benefit.
Plant constituents have been proven useful in the prevention and treatment of a wide variety of diseases and conditions. For example, barley has been shown to be particularly effective in lowering lipid levels in animal models (Qureshi et al., “Suppression of Cholesterogenesis by Plant Constituents”, Lipids, Vol.20, pp. 817-824 (1985)). More specifically, α-tocotrienol has been identified as a therapeutic agent for hypercholesterolemia (Qureshi et al., “The Structure of an Inhibitor of Cholesterol Biosynthesis Isolated from Barley”, J. Biol. Chem., Vol. 261, pp. 10544-10550 (1986)).
High serum cholesterol levels are implicated in numerous diseases and disorders including arteriosclerosis, atherosclerosis, cardiovascular diseases, diabetes mellitus, familial hypercholesterolemia, anorexia nervosa, cirrhosis of the liver, hepatitis and obstructive jaundice. A decrease in low density lipoproteins (LDLs) and/or an increase in the ratio of high density lipoproteins (HDLs) to LDLs will lower the risk of heart disease and retard the progression of the abovementioned diseases and disorders.
It has been found that populations that consume a diet high in certain types of plants, such as cereals and other grains tend to have a low incidence of heart disease and related disorders. This phenomenon was originally attributable to the high fiber content of cereal grains. (Kritchevsky et al., “Fiber, Hypercholesterolemia and Atherosclerosis”, Lipids, Vol.13, pp.366-369 (1978)). However, it has also been found that there are several natural plant components that contribute heavily to the low level of cholesterol and diseases related to hypercholesterolemia. Recently, the hypocholesterolemic effects of cereal grains, which contain tocotrienols (“T3”) and structurally similar compounds, such as tocopherol (“T”), have been noted.
Tocopherols and tocotrienols are two classes of compounds that are known to have a beneficial effect on the level of cholesterol in the bloodstream. They are found primarily in plant material. For example, high levels of tocols are found in crude vegetable oils such as soybean, barley, sunflower, canola, rapeseed, cottonseed, safflower, corn, palm, palm kernel, and rice bran oils. Rice bran and palm oils have particularly high levels of tocotrienols and tocopherols. Typically, palm oil has about 600-700 mg/kg tocols, with about 50% of the total being tocotrienols. Rice bran oil has about 800-900 mg/kg tocols, with about 57% being in the form of tocotrienols.
As a class, the tocopherols, including d-α-tocopherol (vitamin E), have been extensively studied. As a result of these studies, certain biological activities have been attributed to tocopherols. Such activities include platelet aggregation, and antioxidant functions (Niki et al., “Inhibition of Oxidation of Biomembranes by Tocopherol”, Ann. N.Y. Acad. Sci., Vol. 570, pp. 23-31 (1989) and Fukuzawa et al., “Increased Platelet-Activating Factor (PAF) Synthesis in Polymorphonuclear Leukocytes of Vitamin E-Deficient Rats”, Ann. N.Y. Acad. Sci., Vol. 570, pp. 449-453 (1989)). Although the exact structure-function relationship is not known, several experiments have highlighted the importance of the phytyl side chain in the biological activity of tocopherols (Skinner et al., “Antioxidant Properties of α-Tocopherol Derivatives and Relationships of Antioxidant Activity to Biological Activity”, Lipids, Vol. 5, pp. 184-186 (1969) and Diplock et al., “Relationship of Tocopherol Structure to Biological Activity, Tissue Uptake, and Prostaglandin Biosynthesis”, Ann. N.Y. Acad. Sci., Vol. 570, pp. 73-84 (1989)).
In contrast to the tocopherols, interest in the tocotrienols has been limited, as those compounds were not typically considered to be biologically useful. Recently, however, studies have indicated that tocotrienols may be biologically active. For example, U.S. Pat. No. 4,603,142 identifies d-α-tocotrienol, isolated from barley extracts, as an inhibitor of cholesterol biosynthesis (Qureshi, 1986, supra). Various human and animal studies have confirmed the impact of pure tocotrienols, isolated from barley, oats and palm oil, on cholesterol biosynthesis, specifically LDL-cholesterol (Qureshi et al., “Dietary Tocotrienols Reduce Concentrations of Plasma Cholesterol, Apolipoprotein B, Thromboxane B2 and Platelet Factor 4 in Pigs with Inherited Hyperlipidemias”, Am J. Clin. Nutr., Vol. 53, pp. 1042S-1046S (1991); Qureshi et al., “Lowering of Serum Cholesterol in Hypercholesterolemic Humans by Tocotrienols (Palmvitee)”, Am J. Clin. Nutr., Vol. 53, pp. 1021S-1026S (1991); Tan et al., “The Effect of Palm Oil Vitamin E Concentrate on the Serum and Lipoprotein Lipids in Humans”, Am J. Clin. Nutr., Vol. 53, pp. 1027S-1030S (1991)). In addition, γ- and δ-tocotrienols have been indicated for use in the treatment of hypercholesterolemia, hyperlipidemia and thromboembolic disorders (European Patent Application No. 412 419).
The known naturally occurring tocotrienols have been designated α-, β-, γ-, and δ-tocotrienol. These compounds exhibit varying degrees of hypercholesteroemic activity and have also been used as antithrombotic agents and antioxidants. α-T3, for example, displays antioxidant activity against lipid peroxidation in rat liver microsomal membranes and against oxidative damage of cytochrom P-450 (Serbinova, “Free Radical Biology and Medicine” (1991)).
During the process of refining vegetable oils, tocopherols and tocotrienols are generally lost as by-products and waste streams. Tocopherols are found at a level of about 1% to about 20%, and tocotrienols are found at about 0.1% to about 5.0%, in deodorizer distillates, steam refining distillates and articulated soapstocks. These by-products and waste streams, however, also contain many other components. Efforts to isolate tocopherols and tocotrienols in high yields have been unsuccessful. Accordingly, a process for the purification of tocopherols and/or tocotrienols from by-products, waste streams, distillates and soapstocks is desirable. The purified tocols, in particular, tocotrienols, can then be used as pharmaceuticals, in foodstuffs and as dietary supplements.